"He's a leader of his country. I say it's better to get along with Russia than not," Trump said on Fox News Channel's The O'Reilly Factor, adding that Moscow was helping the US in the fight against ISIS and "Islamic terrorism all over the world."
"But he's a killer, though. Putin's a killer." O'Reilly said to Trump in the exchange.
"Lot of killers. We've got a lot of killers. What, you think our country's so innocent?" Trump asked back.
The Fox interview comes as Trump ramped up his criticism of a federal judge who blocked a travel ban on seven mainly Muslim nations and said courts were making US border security harder, intensifying the first major legal battle of his presidency.
The remainder of the interview, which was filmed at the White House on Friday, will air on Monday and Tuesday on Fox News Channel's The O'Reilly Factor.